A washing machine generally consists of an outer casing in which is mounted a water-tight interior container or tub. A perforated drum is commonly mounted inside the tub in a manner which allows the drum to rotate with respect to the tub. During operation, washing liquid is contained within the tub and the laundry to be washed is located within the perforated drum. The laundry is agitated, either by slow rotation of the drum or by the operation of an agitator located within the drum. When the laundry has been washed, some washing liquid is drained from the tub and further washing liquid is extracted from the laundry by spinning of the drum within the interior container to spin washing liquid therefrom. The extracted water exits the drum through the perforations in the wall thereof. Extraction of rinse water is achieved in a similar manner.
It is understood that more water can be extracted from the laundry if the drum is spun at higher spin speeds. There is thus a tendency to spin the drum at as high a spin speed as possible. Increasing the spin speed, however, results in the need for a stronger drum. One way to achieve this is to manufacture the drum with an inner wall and an outer wall. A drum having this type of configuration is illustrated in WO 99/58753. There is a risk, however, that water which is being spun out of the drum during the spinning stage of a washing cycle will be retained between the inner and outer walls of the drum. This would add to the effective weight of the drum and result in excessive consumption of energy.